Known examples of existing electronic components containing coils include a multilayer inductance device described, for example, in Japanese Unexamined Patent Application Publication No. 2007-214424 (Patent Document 1). The known multilayer inductance device described in Patent Document 1 includes a spiral coil conductor made up of internal conductors, a first nonmagnetic layer arranged in such a manner as to be perpendicular to the coil axis of the coil, and second nonmagnetic layers arranged between the internal conductors.
According to the known multilayer inductance device, the coil has an open-magnetic-path structure because the first nonmagnetic layer is arranged in such a manner as to cut across the coil. As a result, abrupt reduction in inductance due to magnetic saturation is unlikely to occur even when a current of the multilayer inductance device is increased. In other words, the direct current (DC) superposition characteristics of the multilayer inductance device are improved.
Meanwhile, there is a case in DC-to-DC converters requiring different inductances of a coil for a low-output-current region and a high-output-current region. More specifically, in an electronic component including a coil used for DC-to-DC converters, DC superposition characteristics are required which allow realization of a relatively high inductance in a low-output-current region and a relatively low inductance in a high-output-current region.
However, because the multilayer inductance device described in Patent Document 1 maintains an approximately constant inductance even when the current increases, it is hard to obtain the DC superposition characteristics suitable for DC-to-DC converters described above.